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Cardiac arrhythmia management by application of adnodal stimulation for hyperpolarization of myocardial cells
| Details |
Inventors: Kieval, Robert S.;
Assignee: Medtronic, Inc. (Minneapolis, MN)
Primary Examiner: Kamm; William E.
Assistant Examiner: Schaetzle; Kennedy J.
Attorney, Agent or Firm: Patton; Harold R., Atlass; Michael B.
An anodal stimulation method and apparatus for the prevention or treatment of tachyarrhythmias using anodal stimulation (AS) energy for effecting hyperpolarization of myocardial cells of a heart chamber to enhance the relaxation thereof in the diastolic phase and to enhance cardiac function, reverse or inhibit cell activation, and thereby treat or prevent tachyarrhythmias. In a preemptive mode with a recognizable ventricular rhythm, the AS pulse is optimally timed to be delivered in an AS delivery interval following an AS delay interval timed from a preceding ventricular depolarization to effect maximal cardiac relaxation and suppress aberrant electrical activity. In a reactive mode responsive to a detected tachyarrhythmia requiring delivery of an anti-tachyarrhythmia therapy, e.g. a cardioversion shock therapy, the AS pulse is delivered during charging of high voltage output capacitors providing the cardioversion shock energy. The sub-threshold AS pulse or train of pulses is increased in energy (amplitude) and/or decreased in energy to and from a peak energy level gradually rather than abruptly. The AS pulses are delivered through a plurality of discrete AS electrodes distributed about the heart chamber or through or large surface area epicardial patch or endocardial AS electrodes. |
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DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The preferred embodiments of the invention are explained hereafter in the context of a comprehensive implantable tachyarrhythmia management system, e.
g.
a PCD IPG and leads, implanted in a patient including large surface area cardioversion electrode(s) in substantial contact with the myocardium.
The PCD system provides programmable single or dual chamber pacing and/or cardioversion/defibrillation capabilities of the types described in detail in commonly assigned U.
S.
Pat.
No.
5,312,441 and the above-referenced '769 application, respectively, incorporated herein by reference in their entireties.
As described below, the system may be simplified into sub-systems for operating in a single chamber or offering fewer therapies by eliminating certain of the components and operating algorithms of the comprehensive system.
Before describing the inventive method and apparatus embodied in the preferred systems, attention is directed to FIG.
1 that depicts the electrical depolarization waves attendant a normal sinus rhythm cardiac cycle in relation to the fluctuations in absolute blood pressure, aortic blood flow and ventricular volume in the left heart.
The right atria and ventricles exhibit similar pressure, flow and volume fluctuations in relation to the PQRST complex.
The cardiac cycle is completed in the interval between successive PQRST complexes and following relaxation of the atria and ventricles as the right and left atria re-fill with venous blood and oxygenated blood.
In sinus rhythm, the interval between depolarizations may be on the order of 500.
0 ms to 1,000.
0 ms for a corresponding sinus heart rate of 120 bpm to 60 bpm, respectively.
In this time interval, the atria and ventricles are relaxed, and overall atrial size or volume may vary as a function of pleural pressure and respiration.
In the blood pressure diagrams of FIG.
1, it may be observed that the atrial and ventricular blood pressure changes track and lag the P-waves and R-waves of the cardiac cycle
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